The control objects model functionality that is not naturally tied to any other object... We do not believe that the best (most stable) systems are built by only using objects that correspond to real-life entities, something that many other object-oriented analysis and design techniques claim... Behavior that we place in control objects will, in other methods, be distributed over several other objects, making it hard to change this behavior.

p. 133 as cited in: "Object Oriented Software Engineering: A Use Case Driven Approach Ivar Jacobson, et al. (1992)", Book review by Ted Felix on tedfelix.com, 2006. - Object-Oriented Software Engineering: A Use Case Driven Approach (1992)